Adipocyte differentiation is coordinatedly regulated by several transcription factors. C/EBP beta, C/EBP delta and ADD-1/SREBP-1 are active early during the differentiation process and induce the expression and/or activity of the peroxisome proliferator activated receptor-gamma (PPAR gamma), the pivotal coordinator of the adipocyte differentiation process. Activated PPAR gamma induces exit from the cell cycle and triggers the expression of adipocyte-specific genes, resulting in increased delivery of energy to the cells. C/EBP alpha, whose expression coincides with the later stages of differentiation, cooperates with PPAR gamma in inducing additional target genes and sustains a high level of PPAR gamma in the mature adipocyte as part of a feedforward loop. Altered activity and/or expression of these transcription factors might underlie the pathogenesis of disorders characterized by increased or decreased adipose tissue depots.